JPH09257788A - Method for non-destructive judgement for creep damage of crmov steel product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge a creep damage by bonding a membrane to the surface of a CrMoV steel product to transfer carbide of the surface part of the steel product to the membrane and peeling this membrane to take out carbide from the surface of the steel material to measure the kind and quantity ratio thereof. SOLUTION: A membrane is bonded to the surface of a steel product to transfer carbide to the membrane and this membrane is peeled to take out carbide and the kind and quantity ratio of carbide are measured to simply and accurately inspect a creep damage degree. Since carbide of the steel product can be sampled by a definite etching method, sampling can be simply and accurately performed without an individual difference of a measuring person. Sampled carbide is analyzed by X-ray analysis to efficiently obtain data in a non- destructive manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive method for determining creep damage, which is capable of accurately and nondestructively determining the degree of creep damage at high temperature parts such as a rotor for power generation, a passenger compartment, and a steam pipe. Is.

[0002]

2. Description of the Related Art Cr widely used in power generation equipment, etc.
It is known that MoV steel material undergoes irreversible aging material damage called creep damage when used under high temperature stress for a long time, and when this creep damage progresses, the safety of equipment constructed of the material is known. Etc. are damaged. By the way, many of the thermal power generation facilities are now aging,
In order to ensure the reliability of equipment (especially high-temperature parts such as rotors and passenger compartments), it is important to accurately and non-destructively evaluate the creep damage of the material constituting the equipment. Conventionally, as a method for nondestructively evaluating the degree of creep damage of a material, a replica method of transferring a metallographic structure of the material to a thin film is known. In the replica method, an A parameter method and a void area ratio method are used. ing. In addition to the replica method, a hardness method and an ultrasonic method are available as test methods.

[0003]

The A-parameter method is the main method among the above-mentioned replica methods, but in order to determine the structure by this method, it is necessary to accurately transfer the structure from the actual machine to the replica film. First, a skillful technique is required to determine the creep cavity from this transferred pattern and quantitatively measure it. The same applies to the void area ratio method. Further, the hardness method has a problem in that when a field test is performed on an actual machine, a hardness meter cannot be installed, or even if it is possible, it cannot be installed horizontally, and an error easily occurs. The ultrasonic method has low sensitivity in the early stage of deterioration (= the void volume ratio is small), and the void may not be detected. The present invention was developed against the background of the above circumstances.
It is an object of the present invention to provide a non-destructive method for determining creep damage in CrMoV steel that can easily and accurately measure the degree of creep damage in power generation equipment and the like made of MoV steel.

[0004]

In order to solve the above problems, the nondestructive method for determining the creep damage in CrMoV steel material of the present invention is to attach a thin film to the surface of CrMoV steel material,
After transferring the carbide on the surface of the steel material to this thin film, peel off the thin film to take out the carbide from the surface of the steel material, measure the type and amount ratio of this carbide, and determine the creep damage based on the measurement result. Characterize.

The steel material targeted by the present invention is so-called CrMoV steel, which contains Cr, Mo, and V as essential components. For example, C: 0.25% or less, Si: 0. 15-0.35%, Mn: 1% or less,
P: 0.012%, S: 0.015%, Ni: 0.75
% Or less, Cr: 1.05 to 1.50%, Mo: 1.0 to
1.5%, V: 0.2 to 0.3%, balance Fe
And other impurities. Further, as the applied steel material, the material which actually constitutes the actual machine is suitable, but in the method of the present invention, it is also possible to target the material before assembling in order to evaluate the creep resistance in advance.

Further, as the thin film used in the present invention, plastic, carbon, or the like can be appropriately used. Further, the thin film may be adhered not only by adhering a thin film prepared in advance to the surface of the steel material, but also by applying a plastic liquid or the like on the surface of the steel material and evaporating the solvent to form the thin film. When depositing the thin film, the surface of the steel material is usually polished and corroded with an appropriate corrosive liquid, but a corrosive liquid having a strong corrosiveness is used so that carbides can be easily taken out. The type of carbide and the quantity ratio (diffraction line intensity ratio) of the carbide transferred to the thin film can be determined by, for example, diffraction using X-rays.
Can be carried out by identifying The quantitative ratio may be determined quantitatively, or may be determined by indicating the degree of the amount.

[0007]

That is, according to the present invention, since the carbides (for example, M ₂₃ C ₆ and Fe ₃ C) of CrMoV steel can be collected by a certain corrosive method, the collection depends on the individual measurer. Can be performed simply and accurately without Then, by analyzing the collected carbide by X-ray diffraction or the like, data relating to the type and amount ratio (for example, X-ray diffraction intensity ratio) of the carbide can be obtained efficiently and nondestructively.

Further, it has been clarified by the study by the present inventors that there is a correlation between the degree of creep damage and the type and amount ratio of carbides. By applying the measured data to this relation, It is possible to know the creep damage degree of the test steel material accurately and promptly. By applying the above judgment method to the actual machine, it is possible to accurately and easily know the degree of creep damage of the steel material used in each actual machine,
Therefore, the degree of creep damage of the steel material can be known at an early stage, and the reliability of equipment using the steel material can be improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. A part of the surface of the device made of CrMoV steel material melted by a conventional method is surface-polished for about 60 minutes by using an abrasive such as diamond paste. The area to be mirror-polished is preferably at least 35 × 25 mm.
Since the polishing time varies depending on the surface properties of the steel material surface, the polishing time is not limited to the above time and the polishing method is not particularly limited.

Next, the polished surface is etched using a polishing solution composed of a 30% nitric acid alcohol solution or a 30% nitric acid + 5% picric acid alcohol solution. Note that other polishing liquids can be used in the present invention.
In this embodiment, as described above, the surface of the steel material is mechanically polished and then chemically polished (etched), but the present invention is not limited to the method and content. In short, it is only necessary that the surface of the steel material can be cleaned so that the carbide can be collected well, and if it is already cleaned, the polishing operation can be omitted.

Next, when the surface of the steel material turns black due to the etching, a thin film made of acetylcellulose is immersed in methyl acetate to adhere to the surface of the steel material so that air bubbles do not enter, and 3 to 5 minutes after the adhesion, the surface of the steel material is Peel the thin film from. In addition, in the present invention, the type of the thin film and the attaching method are not particularly limited. The above-mentioned operations from surface polishing to peeling of the thin film are repeated 4 or 5 times, and each thin film thus collected is placed in a beaker containing acetone and ultrasonic cleaning is performed for 3 to 5 times.
Carry out the carbide from the thin film for 2 seconds. Immediately thereafter, the thin film is removed from the acetone solution. If this work is delayed, the thin film dissolves in the acetone solution to form a jelly, which makes it difficult to separate from the carbide. After taking out the charcoal-based material, the charcoal-based material is left to stand for 10 to 20 minutes to precipitate the charcoal-based material, and the supernatant liquid is extracted with a Komagome pipette or the like. When the supernatant liquid is almost lost, alcohol is added to carry out ultrasonic cleaning. Finally, pour into a suction filter to obtain charcoal on the filter. The filter is dried well, the carbide is identified by X-ray diffraction, and the type and amount ratio of the carbide are derived. In addition,
The method for measuring the carbide is not particularly limited, but it is advantageous to perform the X-ray diffraction as described above, because it is simple and can be performed accurately.

[0012]

[Examples] Sample materials having the components shown in Table 1 were prepared, and each sample material was analyzed for carbides by X-ray diffraction in the same manner as in the above embodiment. In addition, the sample material No. 1 to
No. 5 is the actual equipment of the turbine rotor for the generator, and the sample material No. No. 6 is a steel material for creep test piece and a test material No. 7
Is a steel material for thermal aging.

[0013]

[Table 1]

As a result of the identification of the carbide by X-ray diffraction, M ₂₃
C ₆ type carbides and Fe ₃ C type carbides were analyzed. The X-ray diffraction intensity ratio of these carbides (the intensity ratio of the M ₂₃ C ₆ type carbide to the Fe ₃ C type carbide) was determined, and the results are shown in FIG. 1 based on the relationship with the Larson Miller parameter. The Larson Miller parameters are the temperature T and the elapsed time t.
As a parameter, (T + 273) * (logt + 2
It is expressed by the relational expression (0) and is generally used as an index showing the degree of high temperature service.

As a result of FIG. 1, in each test material, the diffraction intensity ratio increases (the proportion of M ₂₃ C ₆ type carbide increases) as the Larson mirror parameter increases, that is, as the high temperature service increases. It was also confirmed by a transmission electron microscope that coarse M ₂₃ C ₆ type carbides were formed at the grain boundaries in the test material that was used at high temperature. Also, among the test materials, there is a difference in the behavior of the strength ratio change between those that are heated under stress and those that are not, and the time-dependent behavior of carbides varies depending on the stress load. Is recognized. That is, FIG. 1 shows that there is a significant relationship between the change in carbides and the degree of creep damage, and the amount ratio of carbides can be effectively used to determine the degree of creep damage.

[0016]

As described above, the CrMo of the present invention is used.
According to the non-destructive determination method of creep damage in V steel, a thin film is attached to the surface of a CrMoV steel, the carbide on the surface of the steel is transferred to the thin film, the thin film is peeled off, and the carbide is taken out from the surface of the steel. The type and amount ratio of this carbide is measured, and the creep damage is determined based on the measurement result. Therefore, the degree of creep damage of the target steel material can be accurately and easily determined. Can be performed efficiently.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the Larson mirror parameter and the X-ray diffraction intensity ratio of carbide in the test material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Ishiguro 4 Chazu-cho, Muroran-shi, Hokkaido Inside Japan Steel Works, Ltd.

Claims (1)

[Claims] 1. A thin film is attached to the surface of a CrMoV steel material,
After transferring the carbide on the surface of the steel material to this thin film, peel off the thin film to take out the carbide from the surface of the steel material, measure the type and amount ratio of this carbide, and determine the creep damage based on the measurement result. Non-destructive determination method for creep damage in characteristic CrMoV steel